The clonal neuroblastoma cell line, N4TG1, was used to elucidate the interaction of opiate receptors with muscarinic, benzodiazapine and tricyclic antidepressant receptors. It was found that chronic treatment (14 days) of N4TG1 cells with opiate receptor agonists increases their binding capacity for muscarinic agonists without changing the binding capacity for opiate agonist. The mechanism of this interaction is being investigated.